• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.465-468
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• 2006

In the existed study, a fire outbreak in a reinforced concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. Therefore, this study is willing to propose fundamental data for quick and accurate diagnosis of deteriorated concrete structure by fire damage with experiment according to the design compressive strength.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.185-191
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• 2010

To effectively utilize resources of reject ash and dredged soil, globular shape-formed artificial lightweight aggregate were manufactured in 8~10 mm size. Starting materials were changed various grading and composition, sintered at $1050{\sim}1250^{\circ}C$. The specific gravity, water absorptance of artificial lightweight aggregates were measured on the basis of the KS. In this study could make a prediction about application of bloating mechanism by ferrous materials and alkali/alkali-earth oxide at high temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.1-6
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.650-654
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• 1998

Aggregations of 1,1'-diethyl-2,2'-carbocyanine iodide (DCI) and 1,1'-diethyl-2,2'-dicarbocyanine iodide (DDT) in aqueous solution have been investigated by the steady-state absorption spectroscopy. The equilibrium constants for dimerization of DCI and DDT are found to be $(9.8{\pm}0.5){\times}10^4 \;and\; (1.6{\pm}0.5){\times}10^5\; M^{-1}$, respectively, at 293 K. The enthalpy changes for the dimerization of DCI and DDT are -6.7±0.7 and -7.7±0.8 kcal/mol, respectively. The results show that the dispersion force plays an important role in the aggregation of DCI and DDT in aqueous solution. The absorption bandwidth of DCI/ethanol system has been measured as a function of temperature, providing the evidence for no strong interaction between DCI and solvent molecules. The participation of hydrophobic force in driving the aggregation is suggested. For the first time, DCI in aqueous solution is found to form a new aggregate which has both J- and H- bands.

• Nuclear Engineering and Technology
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• v.42 no.2
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• pp.175-182
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• 2010

As part of a fundamental study on the volume reduction of contaminated concrete wastes, the separation characteristics of the aggregates and the distribution of the radioactivity in the aggregates were investigated. Radioisotope $^{60}Co$ was artificially used as a model contaminant for non-radioactive crushed concrete waste. Volume reduction for radioactively contaminated dismantled concrete wastes was carried out using activated heavy weight concrete taken from the Korea Research Reactor 2 (KRR-2) and light weight concrete from the Uranium Conversion Plant (UCP). The results showed that most of the $^{60}Co$ nuclide was easily separated from the contaminated dismantled concrete waste and was concentrated mainly in the porous fine cement paste. The heating temperature was found to be one of the effective parameters in the removal of the radionuclide from concrete waste. The volume reduction rate achieved was above 80% for the KRR-2 concrete wastes and above 75% for the UCP concrete wastes by thermal and mechanical treatment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.33-34
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• 2022

The purpose of this study was to provide basic data for applying oyster shells and egg shells as fireproof cladding materials by substituting fine aggregates for oyster shell powder and egg shell powder, and comparing strength and fire resistance performance. The reason for the high strength was thought to be that the oyster shell had higher strength than the egg shell itself, and both ESP and OSP were measured at a backside temperature of less than 500℃, so it was judged that it could be used as a fireproof coating for steel structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.36-39
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• 2003

In this study, we made the high strength light weight concrete which was composed of the garnet minute powder to be the industry by-product in the YoungJoo region and the artificial light weight aggregate which the high temperature(1100℃) plastic process. The characteristic of the autogenous shrinkage had been considered about strength characteristic and the age passage In the following addition: The concrete's each unit quantity was determined 145,160,175㎏f/㎥.w/b and s/a was determined 30%, 43%, 45%. the each garnet's substitution ratio was determined 0, 10%. In this results, the compressive strength appeared greatly as the unit joining discretion grew bigger. The autogenous shrinkage ratio was increased rapidly until 7th day but it was reduced after 7th day regardless of the mixed factor. The autogenous shrinkage ratio which follows the change of the unit quantity and s/a increased together as the unit quantity and the s/a increases.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.39-42
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• 2004

Carbon nanofiber/Cu composite powder has been fabricated by electroless plating process. Microstructural evolution of the composite powder after heat treatment under vacuum, hydrogen and air environment was investigated. A dispersed carbon nanofiber coated by copper was produced at the as-plated condition. Carbon nanofiber is coated uniformly and densely with the plate shaped copper particles. The copper plates on the carbon nanofiber aggregate during the thermal exposure at elevated temperature in vacuum and hydrogen in order to reduce surface energy. The thermal exposure of the composite powder in air at $400^{\circ}C$ for 3 hours leads to the spherodization of the composite powder owing to oxidation of copper.

• Resources Recycling
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• v.13 no.5
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• pp.37-44
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• 2004

In this study, neodymium oxalate powders were prepared by injecting oxalic acid to the neodymium chloride solution resulted from the acid leaching solution of NdFeB magnet scrap. The effect of experimental conditions on the characteristics of neodymium oxalate powders were investigated. Neodymium oxalate was aggregated by primary particles formed by nucleation, and average size of aggregates was affected by experimental conditions. In a constant volume, increase of reactants affected the average size of aggregate formed by collision of primary particles. In a constant concentration of reactants, agitation speed decreased the size of aggregate due to breakage of particles attached on the surface of aggregate. The number of primary particles decreased with increasing reaction temperature, and the size of aggregates decreased due to the decrease of collision probability. From the results of decomposition behavior of neodymium oxalate, oxalate decomposed from $400^{\circ}C$, and neodymium oxide began to crystallize at above $620^{\circ}C$.

• Journal of Korea Spatial Information System Society
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• v.9 no.2
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• pp.93-107
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• 2007

In this paper, an adaptive range aggregation spatial index method is proposed for spatial range query in ubiquitous sensor networks. As the ubiquitous sensor networks are the new information-oriented paradigm, many energy efficient spatial range query methods in ubiquitous sensor networks environment are studied vigorously. In sensor networks, users can monitor environment scalar data such as temperature and humidity during user defined time and spatial ranges. In order to execute spatial range query efficiently, rectangle based index methods are proposed, such as SPIX. But they define the return path as the opposite of its query transmit path. However, the sensor nodes in queried ranges are closed to each other, they can't aggregate the sensed value in a queried range because their query transmission paths are different. As a result, the previous methods waste energy unnecessarily to aggregate sensing data out of the queried range. In this paper, an adaptive aggregation index method is proposed that can aggregate values in a user defined range adaptively by using its neighbor information. It is shown that sensor power is saved efficiently by using the proposed method over the performance evaluation.